Berkshire Hathaway (BRK.B) - Get Berkshire Hathaway Inc. Class B (BARK.B) Report Chairman and CEO Warren Buffett said on CNBC this morning that he would judge President Trump after four years first and foremost by how safe the U.S. is.

He said his main concern is how to prevent rogue nations from getting weapons of mass destruction, and he singled out North Korea as a specific threat.

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